How do u find a common multiple

1. make a list of multiples for each number

2. continue your list until at least two multiples are common to all lists.

3. Identify the common multiples

he least common multiple, or LCM, is another number that's useful in solving many math problems. Let's find the LCM of 30 and 45. One way to find the least common multiple of two numbers is to first list the prime factors of each number.

30 = 2 * 3 * 5

45 = 3 * 3 * 5

Then multiply each factor the greatest number of times it occurs in either number. If the same factor occurs more than once in both numbers, you multiply the factor the greatest number of times it occurs.

2: one occurrence

3: two occurrences

5: one occurrence

2 * 3 * 3 * 5 = 90 < - LCM

Step-by-step explanation:

3, 9, 21

Solution: List the prime factors of each.

3: 3

9: 3 * 3

21: 3 * 7

Multiply each factor the greatest number of times it occurs in any of the numbers. 9 has two 3s, and 21 has one 7, so we multiply 3 two times, and 7 once. This gives us 63, the smallest number that can be divided evenly by 3, 9, and 21. We check our work by verifying that 63 can be divided evenly by 3, 9, and 21.